Said exchange units are typically used to exchange the energy possessed by a flow of warm gases, i.e. at a higher temperature, originating from an industrial process, to a cold fluid, i.e. at a lower temperature, circulating inside heat exchange elements that comprise the units.
In particular, gases originating from industrial combustion plants are frequently used as the flow of warm gases.
The coolant contained inside the elements of such systems is usually water or saturated or superheated water vapour, in a pressure range typically between 10 and 80 bar and a temperature range typically between 150° C. and 500° C.
The warm gases, on the other hand, have a temperature that usually varies between 100° C. and 1200° C. approximately and, given that they originate from industrial processes of combustion of urban/industrial waste, they contain ashes diffused within their mass, typically in a percentage that can vary between 0.5 gr/Nm3 and 20 gr/Nm3.
In heat exchange units it is known to provide a tube bundle, which is simultaneously crossed on the inside by a first liquid at a lower temperature, known as the coolant, and surrounded externally by a second fluid, at a higher temperature, typically a gas.
However, the ashes contained in the warm gases tend to soil the heat exchange surfaces of the heat exchange elements, i.e. the outer surfaces of the tubes of the tube bundle, thus hindering the heat exchange between the two fluids and irremediably compromising the performance of the units.
For this reason it is periodically necessary to shut down and clean the units, in order to recover optimal working conditions of the same.
Cleaning operations include cooling the unit, the replacement of the parts to be replaced by destructive cuts and the elimination of dust from the surface by means of mechanical abrasion or shaking.
The maintenance operations in any case require technical shutdown times in the order of several weeks, and considerably affect the plants' overhead costs, considering that such maintenance operations are performed with a frequency equal to approximately three times per year.
The need is felt for a heat exchange unit that permits efficient cleaning operations and that is then able to operate continuously for the longest possible period of time, thus reducing the times and frequency of maintenance operations.
The object of the present invention is to provide a heat exchange unit capable of solving the abovementioned state of the art drawbacks.